Allotropes of Carbon – Important Notes for Class 10 CBSE Exams

ALLOTROPES OF CARBON CBSE 10TH CHEMISTRY 

What are Allotropes?

Allotropes are different forms of the same element, which have different properties. 

Existence of a chemical element in one or more physical forms occurring in the same physical state

Diamond and graphite are the two well known allotropes of carbon. 

Diamond 

• Structure:

• Three dimensional network 
• Each carbon atom is bonded to four other carbon atoms 
• Tetrahedral geometry 
• Hard, high refractive index 
• High dispersion of light 
• Crystalline structure 
• Face centred cubic lattice have eight atoms per unit to form a diamond cubic structure 
• Purest forms of crystalline carbon 
• Carbon atoms are sp3 hybridized in diamond 
• Each carbon in diamond is linked to four other carbon atoms via 4 sigma bonds(covalent bonds) Tetrahedral geometry creates a highly stable three dimensional crystalline lattice

Properties of Diamond

• Hardest naturally occuring substance
• Melting point approximately 3570 degree celsius
• Densest and purest form of carbon
• Insoluble in all solvents
• High refractive index
• Low electrical conductivity
• When heated with H₂SO₄ and K₂Cr₂O₇ at 475K, it's oxidized to CO₂.
• Good conductor of heat
  
  
  
  Graphite

• Structure:
• Hexagonally arranged two-dimensional flat layers of carbon.
• Black in color, soft, and slippery.
• Each carbon is linked to three other carbons via sigma bonds.
• Fourth electron forms a pi bond.
• Layers are held together by weak Van der Waals forces.

  Properties:

• Slippery and soft due to its layered nature.

• Good conductor of electricity (due to delocalized electrons).
• Lower thermal conductivity than diamond.
• Black-colored.
• Insoluble in polar and non-polar solvents due to strong covalent bonds.
• On heating with H₂SO₄ and K₂Cr₂O₇ at 475K, it oxidizes to CO₂.
• Does not react with acids or bases.